This invention relates to a method of and an apparatus for inserting weft into a jet loom.
A nozzle mechanism is widely used in both pneumatic and water jet looms. The purpose of such mechanism is to draw the weft thread from a created thread reserve at a requisite time and to present it to an insertion channel and/or a profiled reed with a sufficient initial velocity. At the same time, it is necessary that the nozzle system works economically, that is, with a low energy consumption, that its noisiness is not excessive, and that it causes no imperfections in the weft.
Two types of nozzles are generally known in the state of the art. The first type of nozzle used has an opening in the form of an annulus, the weft thread being fed through the center of the nozzle and the inserting fluid medium, water or air, surrounds the threads. Such first type of nozzle is used generally.
The second type of nozzle, known first of all from the patent literature, feeds the weft thread into the air or water stream from the side. Said second method is simpler but it does not find general acceptance in practice because the necessary bend of the weft does not contribute beneficially to its insertion. Even the first method (nozzle with annulus) does not produce perfect results.
The first problem of today's nozzles of the first type (nozzle with annulus) is air consumption. In an effect to obtain lowest air consumption, designers select the smallest annular area. To obtain this, they select small internal diameters of the nozzle (2 to 3 mm); this causes two problems at the same time. First of all, there is no easy passage for thicker places on the thread, hence the resistances to passage of the thread are variable. This influences the insertion of velocity; also the production of a miniature nozzle where a precisely centered annulus is not easy. Low air consumption is therefor connected with production intricacy, and with unfavorable effects of the nozzle on the thread.
The second serious problem is acceleration of the weft thread within the required time. The relevance of this problem arises first of all in wide looms, with which it is necessary to accelerate the weft thread to a velocity of over 50 m/sec. The designer of standard nozzles with an annulus overcome this requirement by using nozzles of a considerable length, and lately two nozzles one behind the other; however, neither solution is optimum.
The third problem of modern nozzles is noisiness, first of all in air insertion looms.